Penney Backfires on Ackman

About 100 days after Ron Johnson started as CEO of J.C. Penney Co., hedge-fund manager and board member William Ackman put up a slide at an investor conference that said: "Ron Johnson's record of retailing success makes him the ideal leader to fix JCP."

Less than a year later, the former Apple Inc. retail executive is out, sales continue to plunge and a new management team is preparing to undo some of Mr. Johnson's...